Conducting Experiments

Conducting Experiments

1. Types of manipulations

   • Straightforward manipulations
     • Manipulating a variable simply - by presenting material to the participants
     • Ex - memory research
   • Staged manipulations
     • Staging events during the experiment
     • Used when trying to create a psychological state or simulating a real world situation
   • Manipulation strength
     • Making the independent variable maximally different, while keeping everything else the same

2. Measuring the dependant variable

   • Self report measures
     • Use to measure explicit attitudes
   • Behavioural measures
     • Direct observation of behaviours
   • Physiological measures
     • A recording of response of the body
     • Galvanic skin response (GSR)
       • Measures emotional arousal and anxiety
     • Electromyogram (EMG)
       • Measures muscle tension
     • Electrocardiogram (ECG)
       • Measures heartbeat regularity and rate
     • Electroencephalogram (EEG)
       • Measures electrical activity of brain cells
   • Sensitivity of the dependent variable
     • Must be able to detect resulting difference between groups
     • Ceiling effect
       • Task is so easy that everyone does well
     • Floor effect
       • Task is so hard that no one does well

3. Controlling for participant expectation

   • Demand characteristics
     • Any feature that might inform participants of the purpose of the study
   • Filler items
     • Items on a questionnaire that mislead participants about the purpose of the study
   • Placebo group
     • If the placebo and the experimental group equally increase, it is a placebo effect

4. Controlling for experimenter expectation

   • Experimenter bias
     • Aware of the expectations of the study, expecting how participants should perform
   • Single blind procedure
     • Participant is unaware
   • Double blind procedure
     • Participant and experimenter are unaware

5. Pilot study

   • Trial run with a small sample from the larger sample

6. Manipulation checks

   • Checks for construct validity

7. Debriefing

   • Discussing the ethical and educational implications of the study